I have iPhoto 6.0.6 on my iMac. I did a fresh install of Snow Leopard so it was a good opportunity for a clean up. I had about five thousand photos in the Library. I created a new library by launching iPhoto for the first time (in the new install) and then dragged the folders from my old library from a backup folder on an external drive. I then also copied across some folders from the new library to iPhoto v7.1.5 on my MacBook and that updated no problem. I find it useful at times to create new iPhoto Libraries by holding the option key when launching iPhoto, which also presents a choice to open any one of a number of existing Libraries.